Organopolysiloxane emulsion has been used widely in the various industrial fields such as in fiber treating agents, mold release agents, lustering agents, antifoaming agents and hair cosmetics. In the fiber treating field, various treating agents have been proposed to improve properties such as softness or smoothness of fiber products made of various natural fibers or synthetic fibers so as to provide good texture to the fiber products. For instance, a treating agent which mainly comprises a dimethylpolysiloxane or an amino group-containing organopolysiloxane is known. The silicone-type fiber treating agent is emulsified generally with an emulsifier and used as an oil-in-water emulsion. However, when the amino group-containing organopolysiloxane is used in an emulsion form, the emulsion requires stability, particularly shear stability in diluting. Therefore, it was considered to make a diameter of emulsion particles smaller and, to that end, many kinds of microemulsions and production methods therefor have been proposed.
Japanese Patent Application Laid-Open No. Sho-60-127327 describes a method wherein an insoluble emulsifier and water are added to an organopolysiloxane which has a polar group such as an amino group to form a semi-transparent oil concentrate and, then, the concentrate is dispersed rapidly in water. Japanese Patent Application Laid-Open No. Hei-5-98161 describes a method wherein a poorly water-soluble alcohol and a surfactant are added in a mixture of an amino group-containing polyorganosiloxane and water to emulsify. Japanese Patent Application Laid-Open No. Hei-5-209058 describes a method wherein water is added to a mixture of an amino functionalized polyorganosiloxane and a surfactant and stirred to obtain a homogeneous mixture and, then, the mixture is diluted with further water, to which a lower aliphatic carboxylic acid or an inorganic acid is then added to form a water-soluble salt. Japanese Patent No. 2591912 describes a method for preparing a microemulsion by emulsifying an organopolysiloxane together with a diethylene glycol monobutylether. Japanese Patent Application Laid-Open No. Hei-8-73747 describes a method wherein an amino group-containing organopolysiloxane is neutralized with an amino acid and emulsified to disperse. Japanese Patent Application Laid-Open No. Hei-8-73748 describes a method for preparing a microemulsion wherein an amino group-containing organopolysiloxane is neutralized with an amino acid and emulsified together with glycol ether having a short alkyl group having 4 or less carbon atoms such as methyl, ethyl, propyl, and butyl groups to disperse. However, in all of the aforesaid production methods, it is difficult to provide a small particle microemulsion with good reproducibility.
The present inventor proposed, in Japanese Patent Application Laid-Open No. Hei-4-279667, a method to make an amino group-containing organopolysiloxane having polyether groups at the both terminals emulsified with a nonionic surfactant so as to provide a microemulsion which provides excellent softness to a fiber to attain an effect of improving texture, and which has a small diameter and good stability. Further, the present inventor proposed, in Japanese Patent Application Laid-Open No. Hei-11-292977, a method wherein water for phase inversion is added to a mixture of an amino group-containing organopolysiloxane and a nonionic surfactant to emulsify them under high shearing and, then, the obtained non-fluid gel product is subjected to first kneading. Subsequently, an aqueous acid solution is added to the product to obtain a thick paste, which is then subjected to second kneading and, further if need, a dilution water is added and mixed.